In recent years and with the development of membrane technology, membranes have more and more applications in waste water treatment. However, in the application process, particularly in the treatment applications of waste water with high turbidity, the problem of membrane fouling has not been well resolved. With the improvement of membrane material properties and the reduction of membrane price, the control of membrane fouling has gradually become the main factor that limits its extensive application.
In order to improve the evenness of water flow, permeation efficiency, and to resolve the fouling and blockage problems of the applied membrane, the importance of an optimized design for membrane modules has become more and more significant. Particularly during the application of direct filtration of highly turbid waste water with hollow fiber porous membrane, there emerges a module composed of hollow fiber porous membrane that can be directly immersed in a raw water tank or biochemical tank to perform filtration, generally both ends of the hollow fiber membrane bundles are respectively connected with water-collecting boards (tube) that are separated but standing face to face, kept loose without contact, and set in the water to be treated. The mentioned hollow fiber membranes can use known polyvinylidene fluoride, polyethylene, polyvinyl chloride, polypropylene, polyether sulfone or polysulfone materials, etc. Generally, there are independent aeration and cleaning components setup under the membrane module, so the membrane bundles are in a buffeting state to prevent begriming over the membrane surface and guarantee a high flow rate of the porous membrane in the filtering of highly turbid water. The layout form for the mentioned hollow fiber membrane bundles can be in a curtain shape, cuboid shape or cylinder shape.
Immersion type membrane modules have been widely used. The published or approved patents include Chinese patent CN1331124A, CN1509801A, CN1121895C (U.S. Pat. No. 6,630,069) and U.S. Pat. No. 6,790,360. The abovementioned immersion type membrane modules have all resolved the anti-fouling and anti-blockage properties of the hollow porous membrane yarns to a certain degree, prolonging the lifespan and operating cycles of the modules to a certain degree as well. Both ends of the hollow fiber membrane yarns for the abovementioned membrane modules generally were inserted into the sealed water-collecting tubes that are set face to face. Because the membrane yarns inside the membrane modules were not restrained by a shell and although the buffeting freedom of the membrane yarns was improved under the effect of aeration system, in order to prevent the entanglement among the membrane yarns, the length of the membrane modules should not be very long. For example, in U.S. Pat. No. 6,790,360 the optimized length for membrane yarns is suggested to be 0.7 meter.
Even so, immersion type porous membrane modules still have became a trend and direction for membrane module design in the sewage and waste water treatment field, and the membrane module structure and craft have been continuously improved. There is a curtain type immersion module including two vertically arranged upper and lower water-collecting tubes and hollow fiber membrane bundles in the middle. The feature is that the hollow fiber membrane bundle located between the upper and lower water-collecting tubes, could move right and left within a certain range, and the lower water-collecting tube could also shift up and down within a certain range, which provides the membrane bundle with a certain flexibility to improve anti-fouling capability of the membrane module. For another example, US Patent US2004/0188339A1 describes an immersion module type membrane filtration device with an exchangeable membrane module with an aeration tube installed in the membrane bundles. Not only is the maintenance problem for the membrane module to a certain degree resolved and non-stop operation realized, but also the aeration structure of the device and the anti-fouling property of the membrane yarns are improved.
In the above technologies, consideration was not given to the maintenance of the membrane module, the anti-fouling property of the membrane yarns and the technical problem of water productivity for the complete membrane filtration device in all the designs of the membrane modules.
The purpose of this invention is to provide a suspending hollow fiber porous membrane filtration module that can effectively prevent the entanglement of membrane yarns, effectively remove pollutants on the surface of membrane yarns, wherein the membrane yarns do not rupture easily, the membrane modules have a long lifespan with stable water production quality.